According to AICN sources Die Hard 5 will be called Die Hard 24/7, and the new Fantastic Four reboot will be titled Fantastic Four Reborn. I think both titles are pretty lame, but I would think these aren't set in stone so hopefully they will change into something a little better. They might as well just called them Die Hard: Open for Business and Fantastic Four Reboot.
Die Hard 24/7 is being written by Skip Woods who also wrote Swordfist, Hitman, X-Men Origins: Wolverine, and the upcoming A-Team movie. We don't know much about the story other than Bruce Willis and the producers wanted to take it world wide. It is planned to shoot sometime next year.
As for Fantastic Four Reborn the last we heard Michael Green has been hired to write the script, he is a co-producer on the TV show Heroes, Smallville and he also co-wrote Green Lantern. This film was announced the same day that Disney revealed they would be buying Marvel.We still have yet to see how good Green Lantern will be. Producing the film is Akiva Goldsman who is currently involved with a few DC comic book films such as Jonah Hex, The Losers, and Teen Titans.
I wasn't a big fan of the first two Fantastic Four films, and I'm not very excited to see FOX come in a ruin it all over again. Chances are they will reboot the franchise by recasting all of the characters, but still end up with a weak script and a bad movie. I just don't see it being any better than what they have already done. I just don't think they know what to do with these characters.